6.2.2 The Two Parts of Install

Automake generates separate install-data and install-exec
rules, in case the installer is installing on multiple machines that
share directory structure—these targets allow the build system to
install the machine-independent
parts only once. install-exec installs
platform-dependent files, and install-data installs
platform-independent files. The install target depends on both
of these targets.

While Automake tries to automatically segregate
objects into the correct category, the Makefile.am author is, in
the end, responsible for making sure this is done correctly.